Empirical Formula for Sputtering Yield and Z2 Dependence of Its Q Values

Preliminary estimations of sputtering yields for various ion-atom combinations are very important for SIMS and PWI problems. Recently, Yamamura et al.[1] have proposed the empirical formula for sputtering yield at normal incidence. Their formula includes two adjustable parameters, which correspond to Sigmund α and the threshold energy of sputtering. These two parameters were determined by the least square method so as to fit their formula to experimental data. The best-fit values of α show the interesting Z₂ dependence and they factorized α into two parts, i.e., α = Q(Z₂) α_II , where α_II is the average value of best-fit α’s. The main purpose of this note is to investigate this Z₂ dependence of Q value from the viewpoint of nuclear stopping power of low-energy recoil atom.